典型高碱煤灰对氨煤混燃中氨氧化反应特性的影响

Ammonia can be used as a zero-carbon fuel to replace part of coal for co-firing process, which can effectively reduce the origi⁃ nal pollutant emissions of power plants and promote the transformation of coal-fired power plants to coal and ammonia co-firing power plants. However, due to the high nitrogen content in ammonia, the problem of NO_x emission has attracted much attention. In the com⁃ plex coal and ammonia co-firing process, the correlation between NO_x emissions and coal ash is also worthy of further exploration and analysis. High-alkali coal in coal-fired power plants is a kind of coal with broad development prospects, but the emission characteristics of high-content metal oxides on ammonia oxidation reaction are rarely studied. In order to explore the influence of different kinds of high-alkali coal ash on the emission characteristics of ammonia oxidation reaction during the coal and ammonia co-firing process, an ammonia oxidation reaction test platform was built to analyze the variable working conditions, and the two indexes of NH₃ conversion rate and NO generation rate on the surface of various types of coal ash at different temperatures were compared. The specific influence of vari⁃ ous metal oxides in coal ash on the emission characteristics of ammonia oxidation reaction was expounded from two aspects of test results and reaction mechanism. The results show that the main metal oxides CaO, MgO and Al₂O₃ in coal ash can promote the gas-solid ammo⁃ nia oxidation reaction on the surface of coal ash during the coal and ammonia co-firing process, and improve the NH₃ conversion rate. At 400-600 ℃, the promoting effect of coal ash on the conversion rate of NH₃ is as follows: HM-2>HM-1>CJ>AKS>EERDS, which corre⁃ sponds to the order of CaO content in coal ash from high to low, which is basically consistent with the order of MgO. In addition, the above three kinds of metal oxides can promote the directional conversion of NH₃ to NO, and the catalytic effect of CaO is the most significant. Among them, the selectivity of HM-2 with the highest Ca content to NO formation can be increased by 67.86% compared with the pure gas phase ammonia oxidation reaction. CaO and MgO can promote the oxidation of NH₃ and NO on the catalyst surface, which is con⁃ ducive to the rapid production of N₂O the advance of N₂O formation temperature. However, the presence of Na₂O and Fe₂O₃ has an inhibi⁃ tory effect on the oxidation reaction of NH₃, and it has excellent performance in promoting the reduction of NO by NH₃. Among them, the mechanism of Na₂O and Fe₂O₃ promoting NO reduction is not the same.